Method of fixing nitrogen.



J. E. BUGHER.

METHOD 03F FIXING NITROGEN APBLIOAIION FILED MAY 12, 1913: 1,1 1 3,599.

I Patented Oct. 13, 1914.

v i ImgwYw UNITED STATES PATENT OFFICE.

JOHN E. BUCHEB, OF COVENTRY, RHODE ISLAND, ASSIGNOR TO NITROGEN PBODUCTSCOMPANY, A CORPORATION OF RHODE ISLAND.

METHOD orrrxruc NITROGEN.

Specification of Letters Patent.

Patented Oct. 13, 1914.

Original application filed August 8, 1911, Serial No. 642,918. Dividedand this application filed Kay 12,

1913. Serial No. 767,227.

To all whom it may concern:

Be it known that I, JOHN E. BUCHER, a citizen of the United States, andresident of Coventry, in the county of Kent and State of Rhode Island,have invented certain new and useful Improvements in Methods of FixingNitrogen, ofwhich the following is a specification, this applicationbeing a division of the application filed by me August the reacting uponthe nitrid so formed Witha suitable reagent to form ammonia or acompound thereof and preferably to re-form the original salt. The energyconsumed in fixing the nitrogen is, hence, for themost part thatemployed in the electrolytic step of the process and it is desirablethat a salt of such character be used in the initial operation as willreadily yield to electrolytic action with a minimum expenditure ofelectric energy and afiord ametal readily capable of forming a nitrid.With such a metal as calcium or magnesium, the nitrid may be formed at atemperature approximating a dull red heat, and hence such metals are ofspecial value in connection with my process.

The haloid salts are preferred for use in the initial step of my 0 cleprocess, and the nature of the by-pro uct or by-products sought willdetermine whether a chlorid, bromid, iodid, or a mixture thereof shallbe used.

Many attempts have been made to utilize the chlorin of common salt, usedin the ammonia-soda process, for producing bi-carbonate and carbonate ofsoda. Solvay and Mond made many experiments with this end in view but upto the present time none have proven economically successful.

The common practice of todayallows all of the undecomposed common salt,which amounts to about 30 per cent. of the total quantity used, and muchof the chloi'in. of

the decomposed salt to go to waste, some of the chlorin combinedrwithcalcium being recovered and utilized as calcium chlorid.

My invention renders possiblethe saving and utilization of all of theundecomposed common salt, and substantially all of the 'chlorin of thesalt which becomes decomposed, while fiirthermore resulting in anincrease. of approximately one third of the quantity of ammonia presentin the cycle.

The manner of conducting my process in connection with the ammonia-sodaindustry is as follows: The mother liquor from the crude bi-carbonate ofsoda produced in the carbonating tower is evaporated to dryness in anysuitable evaporator; and the free or volatile ammonia is collected bybrine in the usual manner; a residue consisting essentially of a mixtureof dry ammonium chlor d and sodium chlorid being obtained. This mixtureis then heated to the subliming point of ammonium chlorid, to wit, about300 (3., and the ammonium chlorid is condensed to a solid sublimateleaving the sodium chlorid behind in an especially pure condition,suitable for any use, such as table salt, or for strengthening the brineused in the ammonia-soda process; while all of the ammonia correspondingto the decomposed sodium chlorid is thus recovered in the form of dryammonium chlorid. The ammonium chlorid is then brought into contact witha nitrid at the proper temperature, usually a dull read heat. Manynitrids are capable of reacting with ammpnium chlorid, in practicallyall cases with evolution of heat, producin ammonia or ammonium chloridand a chlorid of the metallic base of the nitrid. For example, calciumnitrid reacts, in this connection as follows i i The reaction 1n thlscase evolves sufiicient heat to maintain itself after it has once beenchlorid hereby produced is well suited to serve as an electrolyte in anelectric furnace,

the metals and metal oids-lithium, magnesium, calcium, barium,strontium, aluminium, silicon, etc., and of boron nitrid, is

their power to decompose'water at the ordinary, or at more or lesselevated temperatures, as the case may be, to'form gaseous ammonia, anda hydroxid or metal ormetalloid.

This method of producin ammonia is not economical because the. oxior-hydroxid reoxid' of the maining has littleyalue as such, and must atany reasonable temperature, short of that of the electric furnace, bereduced to the metallic state before it can absorb nitrogen to re-formthe nitrid, and it is very much more difiicult and expensive to reducethe oxids and hydroxids of the nitrid forming metals I than to reducethe haloids of said metals.

have discovered thatnot only do practically all of'the nitrids reactchemically with the mineral acids, but that, they also react with someother hydrogen compounds such as'the acid salts, ammonium salts (aninstance vof .which latter. has been previously given) etc. As anexample of such a reaction involving an acid. salt, I may instancethe'formation of ammonia and magnesium carbonate, or oxid, accordmg tothe following equatlons 2 M ,N,+eNaHoo,=

. 5 tNH,+ 0+ 2+3Nac0. while as -further examples of reactions involving'haloid salts, the base member of which isiammoniumfl may cite:

The foregoing instances will serve to show the value and importance ofthe nitride as used in connectionwith my process. As the 59 process iscyclic in character, the method of cally decomposed, the base memberbeing deposited out and the halogen constituent be-' 60 ing liberated,usually in gaseous form.

Mixture of salts may be-utilized in the furnace, as for exam lemagnesium chlorid may be mixed with so ium chlorid. Further themagnesium or other metal maybe separated as such, or it may be alloyedwith a heavy base metal such as lead, tin, antimony, or mixture ofthese, or similar metals. In any case, the metal or metals whetherdeposited as such or alloyed with other metals, must be capable ofuniting with free nitrogen to form a nitrid or nitrids.

I have found it possible to use lithium, magnesium, calcium, strontium,barium, aluminum, titanium, and the metalloids silicon and boron; butprefer to use calcium chlorid or magnesium chlorid as the haloid salts,because of the abundance and cheapness of these materials, and theparticular facility with which they combine with nitrogen to formnitrids. However, while I prefer calcium and magnesium, I do not confinemyself to any particular nitrid forming element, nor to the use of anyspecific non-metallic element or group of elements to combine with it,e. 9., the iodids, bromids, oxide,-

or similar compounds which may be electrolyzed.

The gaseous halogen given off during electrolysis is in condition to beutilized in the usual Ways, as by absorption with lime to form bleachingpowder, or by compression and cooling to liquefaction. It may also beutilized for the production of oxygen, etc., by absorbing it in milk oflime in the presence of a catalytic agent.

Referring to equations 1, 4, 5, and 6, it will be noted that theammonium is therein, in each case, uncombined after the respectivereactions have been effected. By su plying an excess of the'halogen freeor in tfie form of acid during the course of these reactions, a salt ofammonia may be formed. Thus if, for example, magnesium chlorid beelectrolyzed, depositing netallic magnesium and liberating chlorln gas;this latter may be brought into contact with hydrogen forminghydrochloric acid, and this in turn may be caused to react with themagnesium nltrid formed from the. deposited metal, thus:

Using an excess of hydrochloric acid, the reaction is as follows:

Thus we may readily obtain a supply of the ammonium chlorid used as perequation 4; vthe magnesium chlorid being separated from the ammoniumchlorid by subllmation and the magnesium chlorid being then elec\trolyzed as above. The metal or alloy produced simultaneously with thehalogen is brought into contact with pure nitrogen at the ,propertemperature, generally a red heat, producing a nitrid of the nitrid"forming metal, which nitrid may then be utilized in the ways above setforth.

To summarize briefly the foregoing operations last mentioned: A halo-idsalt of a metal capable of forming a nitrid is electhe halogen elementof the salt. The gaseous halogen may beutiliz'ed for various "purposesbut is preferably treated with hydrogen to form an acid. The nitridforming metal is united with nitrogen, and the so formed nitrid istreated with the acid aforesaid, yielding an ammonium-halogen compoundand a haloid of the nitrid forming metal. These salts are separated, inthe manner above described, which method of separation I regard as ofconsiderable importance and believe the same to be distinctively novelin the connection set forth.'

Finally a quantity of the so formed nitrid is caused to react with theseparated halogen salt to form ammonia and to reform the haloid salt ofthe nitrid forming element, thus completing a cycle of the process. p

I have described my process .in detail with reference to theammonia-soda industry, but it is evident that the same principles areapplicable to other industries, as is evidenced by the followingequation:

The oxids so produced, can then be converted into chlorids by methodssuch as are set forth in the following equations:

the reaction per equation 12 being efl'ected at a strong red heat.

Upon heating, the calcium compound loses its oxygen content, thus:

(14) QCaOCl +heat QCaCI +O completing the cycle. Also, the magnesiumoxid may be electrolyzed to magnesium and oxygen and the magnesium thusproduced combined with nitrogen to complete the cycle by forming thenitrid.

The magnesium oxid may, if desired, be treated with hydrogen and chlorinor with hydrochloric acid to re-form the magnesium chlorid, thus:

completing the cycle. Or the magnesium oxid may be heated with ammoniumchlorid to re-form the magnesium chlorid, thus:

com letin the cycle.

T e caron monoxid of equation 12 may be formed at or even somewhat belowa red heat and it may be converted into carbon dioxid by burning it inoxygen or air. In the latter case free nitrogen may be obtained byabsorbing the carbon dioxid in any of the well known manners, and thisfree nitrogen may be converted into ammonia in the manner abovedescribed, while the carbon dioxid may be used in the carbonating towersof the ammonia-soda process. That it is thus possible to form purecarbon dioxid in connection with said process is of great value, sinceit renders possible the use of smaller carbonating towers, therebyincreasing the efficiency of production as a whole.

The waste nitrogen of the ammonia-soda industry from the carbonatingtowers may also be used in the above cyclic process. From an economicstandpoint therefore my present process is admirably adapted tosupplement many now in use, or it may be operated to advantageindependently.

In view of the variety of applications to which my invention may beapplied I desire it to be understood that I do not wish to be limitedexcept by the scope of the appended claims. In the said claims such anexpression as a substance comprising ammonia is to be regarded as beingof-suflicient breadth to cover ammonia and all compounds thereof.Similarly I regard the term nitrogenous reagent as being applicable tonitrogen or any compound of such element; while the term light metal isintended to embrace such metals as the alkali metals, alkaline earthmetals and aluminum. In the accompanying drawing which forms a parthereof I have shown suitable apparatus in which my novel process may beelfectuated. It is obvious however that this is only by way ofexemplification and I do not desire to be limited thereto in anyparticular.

Referring to said drawings: Figure. 1 is a vertical cross-section of anelectrolyzing apparatus wherein the salt of the nitrid forming metal, 0.9. magnesium chlorid, may be dissociated to liberate said metal. Fig. 2is a somewhat diagrammatic representation of a reaction tube or retortwherein the nitrid forming metal may be reacted upon with a nitrogenousreagent to form a nitrid. This reaction tube further serving, ifdesired, as a receptacle wherein to eflect other reactions involved inthe process.

In Fig. 1,.the potor receptacle 1, may be of iron or other suitablematerial, and contains a mass of fused salt 2, into which project thepositive pole electrode 3 and the negative pole electrode 4. Theselatter may be of any suitable description and material or materials. Theelectrode 3 is preferably inclosed in part at least by a tube or pipe 5,of iron for example, which should be lined with a suitable protectivelining 6. The electrode 4, of course, need not be so protected.

When direct current is passed through'the bath from 3 to 4, the salt ofwhich the bath is composed Will be decomposed, chlorin, for example,being liberated at the electrode 3 and thence escaping through the tube5; While the metal, 0. 9. magnesium will first be deposited at oradjacent to the electrode 4. hen a suflicient quantity of the nitridforming metal has been accumulated it may be withdrawn from the cell orpot 1 via the pipe 7.

The pot is provided with a suitable cover 8, which should be air tight,and the electrode 4 may be insulated from this cover by an insulatingbushing 9.

The metal withdrawn from pipe 7 may be introduced into the reaction tube10, which latter may be heated in any suitable manner as by a number ofBunsen burners 11.

The magnesium 12, for example, in the retort or reaction tube isconverted to a nitrid by passing nitrogen or a suitablenitrogenous'reagent, e. 9., free nitrogen, through the tube, suchreagent passing thereinto from a tube or pipe 13, and the unused portionof the same escaping via tube 14. Cocks or valves 15 may be provided inthese last mentioned pipes.

The halogen, e. g. chlorin escaping from pipe 5, is collected and may becombined with hydrogen, for example, to form hydrochloric acid; and whenthe nitrid of magnesium, for instance, in tube 10, is reacted upon withsaid acid, which may be introduced into said tube in any suitablemanner, as by-injection, at a stage in the process substantially aspreviously described (equations 7 and 8), the ammonia formed may escapethrough tube 14 while the resulting reformed haloid salt will remain inthe reaction tube, from which it may be afterward removed preparatory toagain electrolyzing the same.

Having thus described'my invention. What I claimis:

1. The cyclic method of fixin nitrogen which comprises electrolyzing aaloid salt of a metal capable of forming a nitrid, reacting upon thesaid electrolytically separated metal with a nitrogenous reagent to said'form a nitrid, treating said nitrid with-a hydrogen compound ':;to 5form a,:. substance comprising ammonia and a compound'thebase of whichis the metal'aforesaid, and

said compound with atleast nitrid, treating said nitrid with a hydrogencompound toform a substance comprising ammonia and a compound the baseof which is 'the'metal aforesaid, and reacting upon compound with atleast one reagent to form a haloid salt the base of which is the metalfirst mentioned, said one reagent being halogenous in character.

3. The method of fixing nitrogen which comprises electrolyzing a salt ofa metal capable of forming a nitrid, reacting upon the said electricallyseparated metal with a nitrogenous reagent to form a nitrid, treatingsaid nitrid with water to form ammonia, and reacting upon one of theresidues of this last reaction, other than said ammonia, with at leastone additional reagent to form an electrolyzable salt the base of whichis the metal first mentioned.

4. The method of fixing nitrogen which comprises electrolyzing a salt ofa metal capable of forming a nitrid, reacting upon the said electricallyseparated metal with a nitrogenous reagent to form a nitrid, treatingsaid nitrid with a reagent which includes water forming constituents toform a substance comprising ammonia, and reacting upon one of theresidues of this last reaction with at least one additional reagent toform an electrolyzable salt the base of which is the metal firstmentioned.

5. The cyclic method of fixing nitrogen which comprises electrolyzing ahaloid salt of a metal capable of forming a nitrid, reacting upon thesaid electrolytically separated metal with a nitrogenous reagent to forma nitrid, treating said nitrid with a hydrogen compound to form asubstance comprising ammonia and also an oxygen compound of said metal,and converting said oxygen compound to a simple halogen compound of saidmetal preparatory to reelectrolyzation of the latter.

In testimony whereof I have afiixed my signature, in the presence of twowitnesses.

, JOHN E. BUCH'ER.

Witnesses:

HOWARD C. RIPLEY, NORMAN E. Hour.

